Propeller making



Nov. 29, 1938. J. SQUI ES 2,138,127

PROPELLER MAK ING Filed June 26, 1935 4'Sheets-Shee1'; 1

Nov. 29, 1938. J. SQUIRES 2,138,127

PROPELLER MAKING Filed June 26, 1935 4 Sheets-Sheet 2 INVENTOR. J'oinr Squires.

B Y fi /11411 90 mm. 7 ATTORNEYI5.

' J. SQUIRES Nov. 29, 1938.

PROPELLER MAKING Filed June26, 1935 4.$heets-Sheet 3 f INVENTOR. Join? Squires.

I l p V ATTORNEYS.

Nov. 29, 1938. J. SQUIRES 2,138,127

PROPELLER MAKING Filed June 26, 1935 4 Sheets-Sheet 4 INVENTOR. J07? r? Scouz'ras ATTORNEY5.

Patented Nov. 29, 1938 UNITED STATES PATENT OFFICE PROPELLER MAKING John Squires, Hagerstown,

Md., assignor to United Aircraft Corporation, East Hartford, Conn., a. corporation of Delaware This invention relates to an improved propeller blade and to an improved method and apparatus for making the same. Claims to the improved propeller blade herein disclosed are presented in 5 applicant's co-pending application, Serial No.

213,865, filed June 15, 1938 as a division hereof.

The invention also pertains to improvements in tubular blanks from which propeller blades are formed and to an improved method and apparatus for manufacturing blanks of this kind.

One of the main objects of the invention is to provide an improved method of this character by which the edge portions of a tubular propeller blade may be formed to relatively fine tapered cross sections without cracking the wall structure thereof externally or internally while also avoiding excessive creasing or otherwise injuring the wall of the blade.

Another object-of the invention is to provide a method of this character whereby the leading edge may be brought to a desired rounded contour simultaneously with the formation of a fine trailing edge without injuring the stock from which the blade is formed.

A further object of the invention is to provide for the formation of fins on a tubular propeller blade blank from which leading and trailing edges may be formed and which are so constructed and arranged as to obviate twisting thereof during the bladeforming operation and to guard against changes in the pitch of the blade by the tendency of the edge portion to Y twist the blade after it has been brought to its desired final contour.

Another object of the invention is to provide fins of the foregoing character on a tapered tubular propeller blade blank, which are substantially straight and adapted to be formed to the leading and trailing edge contour of a finished propeller blade during compression of the blank to blade shape.

A still further object of the invention is to provide an improved tubular propeller blade which has substantially flawless leading and trailing edges that conform to propeller airfoil contour requirements, the trailing edge portion having a relatively fine taper.

An additional object of the invention is to provide comparatively inexpensive apparatus by cally formed.

Other objects of the invention are to provide a blade forming method of this character by which a piece of tubular stock is operated upon 1111 such a manner as to form a tubular blank which blades of this character can be economiwhich has preformed fins either on its leading and trailing edge forming portions, or on only one of said edge forming portions; to provide tubular propeller blade blank forming operations whereby the inner and outer surfaces of the 5 blank, particularly at the leading and trailing edge forming portions thereof, may be brought to the contour required to obviate cracking and excessive creasing of the wall structure of the blank during the blade forming operation to which it is subsequently subjected; to provide operations of this character which bring such preformed edge portions to a spiral-like contour conforming with the edge contour of the finished product and conforming in sections substantially to the corresponding sections of the edges of the latter; to provide rolling operations of this kind, which improve the grain structure of the metal of the blank; to provide internal forming operations by which grooves, having rounded sides of prede- 0 termined curvature are formed on the internal side of the wall of the blank in registration with the external fins thereof so as to facilitate the formation of the blank into its final blade shape; and to provide a method of this character by which propeller blades having plain or flanged root end portions can be conveniently formed in accordance therewith.

Further objects of the invention are to provide a tubular .propeller blade blank having register ing internal grooves and external fins on the portions thereof, of which the leading and trailing edges or one of such edges of a finished blade are formed; and to provide leading and trailing edge forming fins on the tubular propeller blade blank which corresponds with the requirements of streamline contour.

Still further objects of the invention are to provide an improved method by which tubular stock is brought to a predetermined tapered con- 4 tour while simultaneously causing flow of the metal to produce a protruding external fin from the metal thereof and forming registering grooves on the inner side of its wall structure; to provide an arbor for this purpose which has ribs protruding from its side surfaces that correspond in cross section and contour with the desired section and contour of the groove; to provide an arbor of this kind which has removable inserts on which the ribs are formed so as to facilitate convenient removal of the arbor from a formed blank and to enable removal and replacement of injured ribs; to provide interchangeable rib inserts of this kind by virtue of which a single arbor may be employed inthe formation of blanks having fins and grooves of difierent dimensions, contour and sections.

Additional objects of the invention are to provide improved apparatus for forming tubular propeller blade blanks of this character by which rough fins can be produced by passing the stock between suitably grooved rolls and later finished in a subsequent rolling operation, which, if necessary, can berelied upon to form the preliminary fins to a state other than that which would allow them to be withdrawn in their rough form from between the initial fin forming rolls; and to provide a finishing operation of this character during which those portions of the blade which were located at the adjacent peripheries of the rolls in the first operation are positioned to be operated upon by the central portions of the peripheries of the rolls used in the finishing operation.

The above being among the objects of the present invention, thesame consists of certain novel features of construction of propeller blades and/0r blanks therefor, and apparatus for producing such blades and/or blanks, and methods and/0r processes and/or steps of methods and/or processes capable of use during one or more of the phases of the operations involved in the production of such blade and blank, as above pointed out, or as will be more specifically brought out in connection with the following description, reference being had to the accompanying drawings forming a part thereof.

Illustrative embodiments of the invention are shown-in the accompanying drawings, in which:

Fig. l is a side elevational view of a. piece of tubular stock suitable for the formation of propeller blade blanks and propeller blades embodying the invention.

Fig. 2 is a transverse sectional view taken on the line 2-2 of Fig. 1.

Fig. 3 is a side elevational view. of an arbor employed in the operation of the propeller blade forming method.

Fig. 4 is a transverse sectional view taken on the line 4-4 of Fig. 3.

Fig. 5 is a transverse sectional view taken on the line 55 of Fig. 3.

Fig. 6 is a side elevational view showing an incomplete propeller blade blank formed to the contour of the arbor shown in Fig. 3.

Fig. 7 is a transverse sectional view taken on the line |--1 of Fig. 6.

Fig. 8 is a transverse sectional view taken on the line 8-8 of Fig. 6.

Fig. 9 is a transverse sectional view taken on the line 9-9 of Fig. 6.

Fig. 10 is a side elevational view, partially in sections, of a piece of stock suitable for forming a propeller blade having a root end portion which differs from the root end portion of the propeller blade formed from the stock illustrated in Fig. 1.

Fig. 11 is a fragmentary longitudinal sectional view showing the stock as it appears after undergoing the preliminary steps of the improved blade forming method.

Fig. 12 is a fragmentary longitudinal sectional view showing the root end portion of a blank made in accordance with the invention reduced in diameter to conform to the dimensions of a blade receiving socket of a propeller hub.

Fig. 13 is a side elevational view of a diflerent arbor which may be advantageously employed in the practice of the improved propeller blade forming method, showing in elevation, a fragmentary portion of a piece of stock suitable for formation upon this arbor.

Fig. 14 is a transverse sectional view taken on the line I4--l| of Fig. 13, showing the stock in' end elevation.

Fig. 15 is a side elevational view of an arbor similar to that shown in Fig. 13, but embodying a further development of the invention.

Fig. 16 is a transverse sectional view taken on the line lG-IG of Fig. 15.

Fig. 1'7 is a side elevational view of a partially formed blank showing the latter as it appears after being removed from the arbor and subjected to an outer end closing operation.

Fig. 18 is a transverse sectional view taken on the line |8-l8 of Fig. 17.

Fig. 19 is a transverse sectional view taken on the line I9|9 of Fig. 1'7.

Fig. 20 is a transverse sectional view taken on the line 20-20 of Fig. 17.

Fig. 21 is a top plan view of a substantially completed propeller blade blank made in accordance with the invention, showing the blank as viewed from above in Fig. 1'7.

Fig. 22 is a vertical sectional view diametrically illustrating the rolling apparatus by which a piece of tubular stock can be formed to the contour of an arbor during the simultaneous formation of the external fins and internal grooves of the blank.

Fig. 23 is a vertical sectional view taken mainly on the line 2323 of Fig. 22, showing the rough forming rolls in elevation and showing portions of the finishing rolls in section so as to illustrate the finishing operation.

Fig. 24 is a transverse sectional view similar to the sectioned portion of the finishing roll shown in Fig. 23, but taken at a different location there- Fig. 25'is a top plan view of apparatus for closing the small end of a tapered tubular blank formed in accordance with the invention.

Fig. 26 is a fragmentary sectional view illustrating the finishing steps in the blank end closing operation.

Fig. 27 is a horizontal sectional view taken centrally through die forming apparatus suitable for bringing a tubular blank to its final blade shape and showing the dies thereof in closed position and illustrating the manner in which the blank is mounted and internally supported. '1

Fig. 28 is a vertical sectional view taken on the line 28-28 of Fig. 27.

Fig. 29 is an edge elevational view of a finished propeller blade made in accordance with'the invention.

Fig. 30 is a side elevational view of the blade illustrated in Fig. 29.

Fig. 31 is a transverse sectional view taken on the line 3l-3i of Fig. 30.

Fig. 32 is a transverse sectionalviewtaken on r the line 3232 of Fig. 30.

Fig. 33 is an enlarged sectional 'vie'wv of a blade formed in accordance with the invention showing the edge portions thereof somewhat in detail.

In the form of the invention illustrated in Figs.

3 to 9 inclusive is illustrated a method and ap-* of cylindrical shape and provided with a radial flange 42 on the extremity, is initially internally supported upon an arbor 43. The arbor 43 has a tapering contour corresponding with the interior contour desired in the finished blank from which the propeller blade is to be formed. Provided on the arbor 43 are integral outwardly extending ribs 44 and 45 which extend mainly longitudinally of the arbor; The ribs 44 and 45 have for their function the formation of grooves of predetermined cross-sectional shape in those portions of a tubular blank from which the trailing and leading edge portions of a finished propeller blade are formed. The end portions of the ribs 44 and 45 at the small end of the arbor are disposed in diametrically opposite' relationship in a horizontal plane as shown in Figs. 3 and 5. In a propeller blade designed for rotation in one direction, successively leftward portions of rib 44 wind upwardly from the central horizontal plane of the arbor and successively leftward portions of the rib 45 wind downwardly from this plane, as viewed in Fig. 3, whereas in a propeller blade designed for rotation in a reverse direction, the wind of the fins would accordingly be in an opposite direction. This formation of the ribs gives them a somewhat spiral course which is predetermined so that the grooves formed thereby in the tubular blank will correspond to the twist of the leading and trailing edge portions of a finished bla'de respectively. In some instances substantially straight fins may be employed in which case they are brought to the desired leading and trailing edge contour of a finished propeller blade in a forming operation of the type hereinafter described.

The cross-sectional shape of the ribs 44 and 45 at successive transverse sections of the arbor also correspond with the cross-sectional shape desired of the grooves formed thereby at corresponding transverse sections of the tubular blank. These ribs preferably have arcuately curved sides which form sides of corresponding curvature on the internal grooves of the finished blank so as to prevent the excessive creasing of the metal at the leading and trailing edge portions of the blank during bending thereof to final bladeshape. In some instances it may be found desirable to provide only one rib on the arbor. Either the leading or trailing edge groove forming rib may be employed alone. Naturally, if only one rib is to be used it is preferable to employ ther ib that forms the groove at the portion of the tubular blank from which the trailing edge portions of the finished blades are formed, for this edge portion of the blade has a much finer cross-sectional taper in the finished blade than the leading edge in order to conform to requirements of airfoil contour.

The first step of the blank forming operation comprises tapering of the tubular stock while internally supported upon the arbor 43 between suitably formed rolls, generally designated in Fig. 22 by the numerals 46 and 41 respectively. These rolls are mounted upon respective shafts having axes substantially in the same vertical plane and they are driven in the respectively opposite directions, illustrated by arrows 48 and 49 in Fig. 22, by suitable driving apparatus (not shown) The peripheries of the rolls 46 and 4! are pro tion thereof, to a minimum depth and radius of curvature corresponding to the outer diameter of the finished tubular blank at the outer smaller end portion thereof.

The eccentricity of successively adjacent portions of the peripheries of the rolls may, if desired, be so predetermined as to taper the wall thickness of the tubular blank from a maximum thickness at its root end portion to a minimum thickness at its outer extremity during the rolling operations or to bring the thickness of the wall to different predetermined values at selected sections of the blank.

The concaved peripheries 50 and 5| of the rolls 46 and 41 have circumferences equal in length to the d stance from the outer side face of the flange 42 to the outer end of the blank. Formed in the inner portion of the wall of the concaved peripheries 50 and 5i are grooves 52 and 53 which correspond roughly in cross section to the cross section of the ribs and 45, respectively, of the arbor 43. These grooves vary in shape at diverse sections of the rolls in accordance with the shape of corresponding sections of the fins of the blank which they are relied upon to form, as well as with respect to the related sections of the edge portions of the propeller blade -which is made therefrom. The grooves 52 and 53 of the rolls 46 and 41 extend diagonally in opposite directions with respect to the widths of the concaved peripheries 50 and 5| of the rolls, respectively, and they are so formed as to register with the ribs 44 and 45 of the arbor 43 during the passage of the arbor between rolls. The cross-sectional areas of longitudinally spaced sections of the ribs 44 and 45 are smaller than the corresponding cross-sectional areas of the grooves 52 and 53, respectively. This difference in area provides space between the walls of the grooves and sides of the 'ribs into which metal of the wall structure of the stock 40 is flowed under the compressive and elongating forces to which the stock 40 is subjected in passing between the rolls preferably while heated to deformable state. In some instances, particularly in the formation of relatively small blanks, the metal stock may be cold worked between the rolls.

Coaxially mounted with the rolls 46- and 41 is a pair of finishing rolls 54 and 55 having complementary concaved peripheries 5S and 51 which also vary circumferentially of the rolls from a maximum depth and radius of curvature corresponding to the radius of curvature of the root end portion of the finished blank, to a minimum depth and radius of curvature corresponding to the radius of curvature of the outer small end portion of the finished blank. The marginal portions 58 and 59 of the rolls 54 and 55 are eccentric with respect to the axis of the rolls and they are so constructed and arranged so as to operate upon the fins of the blank in orderto 1 bring them to a predetermined shape and tapering fineness during passage of the blank between the rolls. The sectioned portion of Fig. 23 iilustrates the manner in which the marginal portions 58 and 59 operate upon the fins at the root end portion of the blank and the sectional view shown in Fig. 24 shows the relation of these marginal portions with respect to the portions of the fins at the small end of the blank. These marginal portions of the rolls 54 and 55 vary in radii between the root end of the blank and the small end thereof in such a manner as to correspond with the wind of the fins between the two extremities of the blank.

In the formation of the piece of tubular stock 40 into a tapered finned blank, the stock is heat-- ed to a desired state of plasticity and then mounted on the arbor 43, as shown in dotted lines at 60 in Fig. 22 with the flanged extremity of the stock adjacent a shoulder 6! on the left end portion of the arbor. The arbor and stock are then extended between the rolls 46 and 41 while the latter are disposed with the deepest portion of their concaved peripheries substantially in vertical alignment with the axes of the rolls. This operation is performed while the stock is heated to a readily deformable state and only substantially one-fourth of the length of the stock is positioned to be operated upon in the first step. When the tubular stock 40 is located in the dotted line position shown in Fig. 22 with its right end located at 62, the rolls 46 and 4! are driven in the directions of the arrows 48 and 49, respectively, thereby working the stock toward conformity with the exterior of the arbor and elongating the stock. After the first pass of the stock between the rolls 46 and 41, the arbor with the stock thereon is removed from the latter rolls and turned with respect to its axis throughout substantially ninety degrees and it is then fed between the finishing rolls 54 and 55. The stock may be brought to conformity with the entire length of the arbor in any desired number of passes but it is preferred to employ four passes before each of which the stock and arbor are advanced substantially one-fourth of the original length of the stock, it being understood that the stock is subjected to treatment between the finishing rolls after each pass between the rough forming rolls. The stock alone, or the stock and the arbor, may be heated between such passes between the successive pairs of rolls, if necessary, to maintain a desired plasticity of the metal. Suitable indexing apparatus is provided for bringing the arbor and stock to the same angular position relative to the peripheries of the rolls before each pass therebetween. Although this apparatus may comprise a large variety of different embodiments, a simple pointer designated by the numeral 63 in Fig. 22 and a notch 64, or other suitable mark on the arbor which. may be conveniently indexed with the pointer, will serve this purpose. a At the end of the rolling operation the blank conforms to the tapered contour of the arbor 43 as illustrated in Figs. 6 to 9, inclusive, wherein' the blank is generally designated by the numeral 64. and 41 form the trailing edge fin, designated by the numeral 65, and the leading edge fin designated by the numeral 66. The leading edge fin 66 preferably has a rounded contour and it registers with an internal groove 61 formed by the rib 44 of the arbor. The trailing edge fin 65 is substantially solid and has a tapering cross section terminating in a comparatively fine outer edge portion. The fineness of the outer edge portion of this fin varies at spaced longitudinal cross sections of the blank as illustrated in Figs. 7, 8 and 9, so as to predetermine the shapes of the leading and trailing edges of the blade subsequently formed from the blank at corresponding transverse sections of the finished product. Registering with the trailing edge fin 65 is an internal groove 68 which is preferably of rounded cross section. This groove and the'groove 61 permit forming of the blank to the final blade The related grooves and ribs of the rolls 46 shape by compression in a subsequent operation without weakening the metal at the edge portions of the finished product by excessive creasing of the metal at such edge portions.

The arbor 43 is then removed from its position within the tapered blank shown in Fig. 6 by the use of any suitable arbor press and the small end of the blank is closed in any desired manner.

When the ribs 44 and 45 are formed integral with the arbor, they preferably extend to the shoulder 6| thereof so as to provide for the accommodation of the passage of root end portion of the blank over the ribs of the arbor. The effect of the portions of the ribs immediately adjacent the shoulder 6| upon the root end portion of the blank can be removed by suitable swaging operations to bring the root end portion thereof to a regular contour. The small end of the arbor may be closed by any. suitable apparatus and method, such, for example, as that shown in Figs. 25 and 26. In this operation the blank 64 is internally supported by a mandrel 69 having a head portion 10 which extends to within a short distance of the small open end of the blank. The mandrel 69 with the blank 64 thereon is then mounted in a suitable lathe or other turning machine which includes a bed H upon which is longitudinally movable a mainslide 12 upon which is supported a compound slide 13. The nose end of the blank may be suitably supported as by a steady rest 14. In case the fins 65 and 66 extend beyond the steady rest, it will be necessary to provide the steady rest with a supplementary member 14 rotatable therein and suitably slotted for accommodation of the fins. The mandrel 69 and blank 64 are rotated in the lathe and a flame from a torch 15 is played upon the end portion of the blank to bring it to a suitable condition of plasticity. The carriage 12 is moved to the right and a spinning tool 16 carried by the compound slide 13 is then brought to a position such that when it is swung about the axis 1'! of the compound slide it will engage the extreme end portion of the blank. As soon as the nose end portion of the blank is heated to a desired degree the compound slide 13 and 4 tool 16 are swung about the axis 11, preferably in a counter clock-wise direction, as viewed in Fig. 25 and the nose or tip of the blank is spun in as indicated in this figure. The spinning operation is continued until the small end of the blank is completely closed, as illustrated in Fig. 26. During this operation the flame from the torch 15 continues to play against the tip end of the blank and to maintain the same at such temperature that when the end is finally closed the metal thereof will weld itself together at the line or point of closure.

In place of the arbor 43 shown in Fig. 5, a similar arbor 43' shown in Figs. 13 and 14, may be used. The arbor 43' corresponds in shape with 00 the arbor 43, but in place of having integral ribs, it is provided with dovetailed grooves 18 and 19 in which inserts 80 and 8|, respectively, are slidably mounted. The grooves 18 and 19 and their respective inserts 80 and BI extend in a. somewhat spiral course corresponding to the wind of the edge portions of the finished propeller blade which is subsequently formed from the tubular blank, designated by the numeral 64'. The insert 70 8D has a projecting rib 44' which provides a groove 61' in the blank 64', and the insert 8| has a projecting rib 45' which forms a groove 68' in the interior of the tubular blank. The grooves 61' and 68' are provided at these portions of the blank 84 from which the leading and trailing edge portions, respectively, of the blade are formed.

In the form of the invention illustrated in Figs. 15 and 16, the arbor 88 is provided with axially extending dovetailed grooves 84 and 85, which are relatively wider than the grooves 18 and 18 of the arbor 48. Slidably mounted in the grooves 84 and 85 are inserts 88 and 81, respectively, on which ribs 88 and 88 are provided for forming grooves in the leading and trailing edge forming portions of a tubular blank. The ribs 88 and 88 extend diagonally with respect to the widths of the inserts 86 and 81, respectively, so as to provide grooves which wind in accordance with the course followed by the leading and trailing edge portions of a finished propeller blade.

The blank forming operation is substantially the same when arbors 48' and 88 are used as set forth previously in the discussion of the operation involving the use of the arbor 43 as shown in Fig.

5. A piece of tubular stock such as that shown at 48, may be mounted upon either the arbor 48' or 88 and then subjected to the foregoing rolling operations between the pairs of rolls 46 and 41 and 54 and 55. In some instances preformed tubular stock of the character shown at 88 in Figs. 13 andl'i may be used to advantage, particularly when two ribs of relatively large radial dimensions are used. The stock 88 includes a metal tube having outwardly extending recesses 8| and 82 formed in opposite side portions for initially accommodating the ribs 44' and 48. Such preformed stock may also be employed to advantage in some instances when one or two,

. either integral or removable ribs are provided on I the arbor. When the ribs of the arbor are carried by shiftable and removable inserts such as the inserts 88 and 8| of Fig. 14 and 88 and 81 of Fig. 16, it is not necessary to extend the ribs all the way to the shoulder 8| of the arbor for during removal of the arbor from the blank after the rolling operation the inserts shift relative to the arbor toward the small end of the blank as the blank is removed until their innermostends reach a position midway between the ends ofethe arbor at which the latter is of small enough diameter to permit outward movement of the combined thicknesses of the inserts and remaining portion of the arbor through the root end portion of the blank. The shiftable rib carryirig inserts may also be moved relative to the arbor'in some instances during the successive passes between the rolls in order to work the stock from which the blank is formed gradually in successive steps to the contour of the full length of the arbor.

'After the rolling operation the arbor 48' is removed leaving the blank in the form shown in section in Figs. 18 and 19 and having leading and trailing edge fins 88' and 85'. These fins vary in cross section at successive sections of the blank in accordance with correspondingcross sections of the leading and trailing edges of the finished propeller blade. The trailing fin 88' is preferably wider and of more tapering contour than the leading fin in order to fulfill the requirements of air foil contour. When the arbor is removed the small end portion of the blank is flattened in the plane of the adjacent end portions of the fins 88' and 88' and this flattened end portion 88 is heated in any suitable manner sufficiently to. weld together the superimposed layers of metals of which it consists into an integral structure. The flattened end portion 88 of the blank may then be cut to any desired shape, as for example, upon the dotted line 8| shown in Fig. 21.

In the formation of a tubular blank for a propeller blade of the type that does not have a flange on its root end portion, a piece of plain cylindrical stock generally designated by the numeral 48' in Fig. is used in place of the stock 48 shown in Fig. 1. The stock 48 may be subjected to the rolling operation while internally supported on any of the foregoing arbors in order to form internal grooves and external registering fins. After the stock 48' is removed from the arbor its small end may be closed in any suitable manner and the root end portion may be reduced by the aid of dies or other suitable means to any desired diameter for reception in,the socket of a propeller blade hub.

By the term tubular blank, as used herein and in the claims, is meant any suitable hollow or shell-like structure, regardless of its crosssectional or longitudinal sectional contour. When the tubular blank is completed it is then compressed to blade shape between suitable dies with the fins and grooves of the blank disposed so as to register with the leading and trailing edge forming portions of the dies, respectively. One form of compression dies and associated apparatus is shown in Figs. 27 and 28, which also illustrate the manner in which a tubular blank of the throughout its entire length and breadth. Thepassages 88 are provided with a communicating inlet and outlet (not shown) which, in practice, are connected to a convenient source of water supply and drain pipe, respectively.

Formed on the front corner portions of the lower die holder 82 are upright posts 81 of substantially rectangular cross-section. An upper die holder 88 having a recess 88 which is complimentary to the recess 88 of the lower die holder is mounted in superimposed relation thereon. The opposite front corner portions of the upper die holder are provided with recesses I88 for slidably receiving the posts 81, which are preferably formed integral with the lower die holder.

Seated in the recesses 88 and 88 of the die holders 82 and 88 are dies MI and I82, respectively,

having longitudinally extending blade forming placement by the inclined walls of their recesses.

The upper die holder 88 is suitably cored to provide cooling medium passages similar to the passages 88 of the lower die holder.

A pair of parallel plates I85 are located adjacent the outer sides of the upright posts 81 and are rigidly secured thereto by bolts I88. The plates I88 protrude beyond the outer ends of the die holders and they are provided attheir outer extremities with'inwardly extending cleats I81,

which are secured in place by bolts I08. The cleats I 01 form channel ways between their inner sides and the front edges of the posts 91 in which side flanges I09 and I I0 of a channel shaped support or cross head II2, having a web II4, are slidably received. As best shown in Fig. 27, the inner edge portions of the flanges I09 and I I0 are provided with recesses I I6 in which shoes I I8, preferably comprising rectangular metal bars, are seated. The shoes II8 carry pins I20 which are received in apertures I22 formed in the posts 91 of the lower die holder 92 and the shoes are yieldably held in spaced relation to the posts 91 by springs I24 which surround the pins I20 and are seated in recesses in the forward edges of the posts and surrounding the apertures I22. These shoes II8 normally bear upon the cross head II2 urging the same outwardly against the inner sides of the cleats I01.

As best shown in Fig. 28, the entire cross head H2 is yieldingly supported on coil springs I28, which are seated upon the lower platen of the press. The springs I28 normally hold the cross head H2, and the blank 84' when supported thereby, more or less centered between the dies and out of contact with both dies.

The web II4 of the cross head H2 is provided with an enlarged central opening I30 of circular contour in which a collar I32 for receiving the shank portion of the blank 64' is detachably mounted. The collar I32 is provided with suitable slots (not shown) between which the flattened portions adjacent the leading and trailing edges of a finished blade may move to permit removal of the latter from the forming apparatus. The cross head II2 serves as the sole support for the propeller blade blank before the dies are brought together and by virtue of the springs I28 it locates the blank in spaced relation between the dies so as to prevent cooling of localized areas of the blank before compression thereof to blade shape.

In supporting the blank internally by pneumatic or other fluid pressure after it is positioned in the collar I32, it is necessary to form a communicative connection between the open end of the blank and a source of pressure in a brief time interval in order to prevent excessive cooling of the blank before the forming operation. This is successfully accomplished by providing the connecting means on a breech block I38 which is swingably mounted on a vertical breech block pin I40, that is mounted in brackets I42 on the flange IIO of the cross head II2. A relatively positive seating of the air inlet I56 on the flange II5 should be provided. This may'be accomplished by a suitable washer or other contacting member, or the contacting member may be somewhat resilient, Such a resilient seating device is illustrated as provided by the sylphon or bellows I46, but this may not be essential. The inner side of the breech block I38 has a recess I44 in which the outer end of a metallic bellows or sylphon I46 is suitably secured in sealed relation therewith. Mounted on the inner end of the bellows or sylphon M6 is a head I48 having a. central protruding boss which is received in the open end of the tubular blank 84'.

Leading to the interior of the bellows I48 and formed in the breech block I38 is an aperture I52 in which a nipple of an outwardly extending valve I 54 is mounted. The valve I54 communicates through a flexible connection with a source of pressure (not shown) and when open supplies air or other gas under pressure to the interior of the bellows I46 and from the latter to the interior of the tubular blank through a restricted orifice I 58 in the head I48 of the bellows. The side of the head I48 within the bellows I48 is larger in area than the end of the boss which extends into the open extremity of the blank and therefore a force differential is created by the pressure on the opposite sides of the head I48 which presses the gasket I50 upon the flange II5 of the blank with a pressure of large magnitude, thus forming an effective seal at the open end of the blank. Any leakage which may occur from the interior of the blank tends to increase this force differential and accordingly increases the pressure upon the extremity of the blank preventing continued leakage. In practice, with the pressure of 300 pounds per square inch in the blank, a. load of 6000 pounds may be exerted on the flange by suitably proportioning the parts I referred to, thus tending to insure suflicient pressure within the blank to cause it to hug the dies when they are closed.

As best shown in Fig. 27, the breech block is releasably held in a closed position by a latch device which includes a vertical cylindrical bar I58 journaled in bearings I60 mounted on the flange I08 of the cross head II2. This bar is provided with an axially extending V-shaped groove in its surface and it is provided with an outwardly extending radial pin I62 by which it may be rotated to bring the V-shaped groove into registration with a protruding edge portion I84 on the free side of the breech block. Adjacent the projecting lip I84 of the breech block is a recess I88 in which the cylindrical portion of the bar I58 is received when the latter is held in locking position by the spring I88 engaging the pin I62. The breech block may be unlocked and swung to open position by moving the pin I82 against the tension of the spring I68 and so rotating the bar I58 in a counter clockwise direction to allow the projecting lip I64 on the breech block to pass by the groove in the bar I 58.

In operation, either the upper or lower die holders may be moved so as to bring the dies together, but the lower die holder I 50 is preferably lifted verticaly upward with, substantial force by mechanism (not shown) of the character customarily used in die forming operations. A tubular blank 84 of the type shown in Fig. 30, having a flange I I5 on its open end is heated to a workable temperature, and is lifted preferably by tongs inserted in the open end of the blank and inserted through the central opening in thereplaceable collar I32 while the cross head II2, lower die holder I50 and upper die holder 88 are spaced apart, and while the breech block I 38 is open.

Before the die holders and dies therein are brought together to compress the blank to blade shape, the valve I54 is opened so as to admit air to the bellows I48 and to supply air to the interior of the tubular blank. The blank is then compressed, preferably by moving the lower die holder upwardly. During this operation precaution is taken to bring the flns 65' and 88' of the blank 64, or the fins and 66 of the blank 64, depending on which blank is used, into proper registration with the portions of the dies IOI and I02, which form the trailing and leading edge portions I12 and I10 of the finished blade I13. The trailing edge I12 is preferably formed to a finely tapered cross section, as illustrated in Fig. 33, in order to bring the blade into accurate conformity with stream line requirements and the leading the blank to the contour of the wind or pitch of the blade during the blank forming operations. Although probably the greatest advantage is de- -rived from forming the trailing edge portion of a propeller blade in accordance with the above method considerable benefit is gained in many instances by also forming the leading edge'in this manner for the curvature of the latter may be predetermined without injuring the wall structure of the blade and the leading edge may be conveniently brought to a greater thickness than the remaining portions of the walls of the blade so as to render the leading edge more rigid and resistant to deformation.

When the propeller blades having different pitches as required for propellers that are designed for operation at different speeds, are to be formed from blanks of the same character, the fins of blanks can be made substantially straight and then later brought to the desired leading or trailing edge contour in the blade forming operation.

Although but several forms of the invention have been illustrated and described in detail, it will be apparent to those skilled in the art that various modifications may be made without departing from the scope of the appended claims.

1. The method of forming a fin on a metal tubular structure, which comprises internallysupporting said structure on an arbor having a rib extending from its periphery, forming a fin from some of the metal of the wall of said structure by passing the latter while internally supported on said arbor.between rolls having arcuately concaved peripheries suitably formed to accommodate the metal of said fin and por tions of the rib of said arbor, and withdrawing said arbor thereafter.

2. The method of forming a finned tapering tubular structure which comprises internally supporting a piece of tubular metal stock on a tapered arbor having a rib extending from its periphery, and forming said stock to the contour of said' arbor and simultaneously grooving. the inte-.

rior of said stock and extruding some of the metal of the wall structure thereof by passing said stock and arbor between rolls having complementary tapering concavities in their peripheries at-least one of which having a recess extending inwardly from its periphery to accommodate the metal of said fin and portions of said rib.

3. The method of forming a tubular propeller blade blank which comprises internally supporting a piece of tubular metal stock on an arbor conforming in exterior contour to the contour desired in the interior of a finished blank, and having a rib so disposed thereon as to register with those portions of the finished blank;

from which one edge portion of a propeller blade is formed, and forming'sald piece of stock to the contour of said arbor and simultaneously flowing some of said metal outwardly to produce an external fin from the metal of the wall structure of said stock and forming an internal groove in registration therewith at those portions of the finished blank from which a selected edge of a propeller blade is formed.

4. The method of forming a tapered tubular propeller blade blank which comprises internally supporting a piece of tubular metal stock on an arbor conforming in exterior contour to the tapered contour desired in the interior of a finished blank, forming said piece of stock to the contour of said. arbor and simultaneously flowing outwardly some of said metal along a course extending mainly in the direction of the length of said'stock but winding slightly with respect to the longitudinal axis thereof and outwardly into angularly demarked relationship with respect to the adjacent metal of said stock to produce a spiral fin from the metal of the wall structure of said stock at those portions of the finished blank from which a selected edge of a' propeller blade is formed, and passing the resulting finned and tapered stock between finishing rolls having complementary concaved peripheral portions engageable with the body portion of said stock and a marginal peripheral portion engageable with said fin.

5. The method of forming a tapered tubular propeller blade blank which comprises internally supporting a piece of tubular stock on a tapered arbor conforming in exterior contour to the contour desired in the interior of a finished blank, forming said piece of stock to the contour of said arbor and simultaneously producing a spiral fin from the metal of the wall structure of said stock at those portions of the finished blank from which a selected edge. of a propeller blade is formed, by passing said stock and arbor between forming rolls having complementary arcuate concavities in their peripheries conforming to the contour desired in the exterior of said finished blank and being suitably formed to accommodate the metal of said fin, and simultaneously finishing the body portion of said blank and opposite sides of said fin by passing the resulting finned and tapered structure between finishing r'olls having opposed concaved and cylindrical peripheral portions""respectively suitably formed to simultaneously finish opposite sides of said fin and the body portion of'said blank.

6.- The method for forming a tubular propeller blade blank which comprises internally supporting a piece of tubular stock on an arbor conforming in exterior contour to the contour desired in the interior of a finished blank, and having a rib so disposed thereon as to' register with those portions of the finished blank from which one edge portion of a propeller blade is formed, forming said piece of stock to the contour of said arbor and simultaneously producing an 'external fin from the metal of the wall structure of said stock and forming an internal groove in registration therewith at those portions of the finished blank from which a selected edge of a propeller blade is formed, and passing the repeller blade which comprises forming a piece of Y metal, stock into a tapered hollow shell-like blank structure and providing a longitudinal fin thereon extending in a generally spiral course corresponding to the wind of an edge portion of the finished blade and projecting outwardly into demarked relationship with respect to the main body portion of said stock, and compressing said blank to blade shape between suitably formed dies with the fin of said blank" disposed at the portions of said dies which form an edge of said propeller blade.

8. The method of forming a tubular propeller blade having a substantially solid finely tapered trailing edge which comprises forming a piece of tubular metal stock into a. tapered tubular blank having a substantially solid fin extending in a course corresponding to the wind of the trailing edge of the finished blade, and compressing said blank to blade shape between suitable forming dies with said fin disposed at the trailing edge forming portions of said dies.

9. The method of forming a tubular propeller blade having substantially solid trailing and leading edges of predetermined cross sections which comprises forming a piece of tubular stock into a tapered tubular blank and providing fins on said blank varying and corresponding in cross section to said predetermined cross sections and extending in courses corresponding to the wind of the trailing and leading edges of the finished blade respectively, and compressing said blank to blade shape between forming dies with said fins disposed at the trailing and leading edge forming portions of said dies respectively.

10. The method of forming a tubular propeller blade having a substantially solid edge portion of predetermined cross section and having a predetermined internal contour at the junction of the sides of said blade and said edge portion which comprises forming a piece of stock into a tapered tubular blank and providing the same with an external fin corresponding in cross section to the predetermined cross section of said edge portion and with an internal registering internal groove corresponding-in contour to said junction and extending in a course corresponding to the wind of said edge portion of .the finished blade, and compressing said blank to blade shape between dies with said fin and groove disposed at the portions of said dies which form said edge portion.

11. The method of manufacturing a tubular propeller blade which comprises forming a piece of metal stock into a tapered blank and providing thereon a fin projecting outwardly in angularly'demarked relationship with respect to the external surface of said stock and extending mainly longitudinally thereof, and compressing said blank to blade shape between forming dies with said fin disposed at the portions of said dies which form an edge of said blade.

12. The method of manufacturing a tubular propeller blade which comprises forming a piece of metal stock into a tapered tubular blank having an external fin extending mainly longitudinally of said blank and having an internal groove registering with said fin and compressing said blank to blade shape between forming dies with said fin and groove disposed at the portions of said dies which form an edge of said blade.

13. The method of manufacturing a hollow propeller blade which comprises forming a piece of metal stock into a tapered hollow shell-like blank structure having fins on its opposite sides extending mainly longitudinally of said blank and projecting in angularly demarked relationship with respect to the external surface thereof, and compressing said blank to blade shape between forming dies with said fins disposed at the leading and trailing edge portions of said dies respectively.

14. The method of manufacturing a tubular propeller blade which comprises internally supporting a piece of tubular metal stock on a tapered arbor, forming said piece of stock to the contour of said arbor and simultaneously extruding a fin from the metal of the wall structure of said stock extending mainly longitudinally of said arbor, and compressing the resulting finned and tapering tubular structure to blade shape between forming dies with said fin disposed at the portions of said dies which form an edge of said blade.

15. The method of manufacturing a tubular propeller blade which comprises internally supporting a piece of tubular metal stock on a tapered arbor, forming said piece of stock to the contour of said arbor and simultaneously extruding a fin from the metal of the wall structure of said stock extending mainly longitudinally of said arbor by passing said stock and arbor between forming rolls having complementary concavities in their peripheries conforming to the contour of said arbor and being suitably formed to accommodate said extruded metal, and compressing the resulting finned and tapering tubular structure to blade shape between forming dies with said fin disposed at the portions of said dies which form an edge of said blade.

16. A propeller blade blank including a tapered hollow shell-like metal structure, andan external fin protruding therefrom in angularly demarked relationship with respect to the external surface thereof and extending mainly longitudinally of said tubular structure.

17. A propeller blade blank including a ta- 'pered hollow shell-like metal structure, and an external fin protruding therefrom in angularly structure, and an external fin projecting from demarked relationship with respect to the external surface thereof and extending mainly longitudinally of said structure, said fin having successive transverse cross sections substantially similar in contour to the corresponding crosssectlons of an edge of a finished propeller blade.

18. A blank for forming a tubular propeller blade including a tapered tubular metal structure having an internal groove in its wall extending in a course corresponding with the wind of an edge portion of a finished blade, and a fin on said tubular structure registering with said.

groove and protruding outwardI' and in angular demarked relationship with respect to the portion of said structure, from which an edge portion of said propeller blade is formed.

21. A blank fon forming a hollow propeller blade including a tapered hollow'shell-like metal structure, and an external fin projecting from the portion of said structure, from which an edge portion of said propeller blade is formed, said fin having successive cross sections corresponding ollow propeller to the requirements of stream line contour and to the shape of related sections of said edge portion of said propeller blade.

22. A blank for forming a hollow shell-like propeller blade including a tapered tubular metal structure, and an external fin projecting from the portion. of said structure, from which the trailing edge portion of said propeller blade is formed, said fin having successive finely tapered cross sections corresponding to the requirements of airfoil contour and to the shape of related sections of said edge portion of said propeller blade.

23. A blank for forming a tubular propeller blade including a tapered tubular metal structure, and an external fin projecting from the portion of said structure, from which the trailing edge portion of said propeller blade is formed, said tubular structure having an internal groove registering with said fin for facilitating deformation of said blank to blade shape.

24. A blank'for forming a tubular propeller blade including a tapered tubular metal structure, and integral fins projecting from the portions of said structure from which the leading and trailing edge portions of said propeller blade are formed, successive cross sections of said fins being similar to corresponding cross sections of the leading and trailing edge portions of said propeller blade respectively, and each of said fins extending in a course conforming to the course of one of the edge portions of said propeller blade respectively.

25. Apparatus for forming a piece of tubular stock to a spirally finned tapering contour including an arbor insertable into said stock conforming to'the desired contour thereof and having a spiral fin forming rib extending from its outer surface, a pair of rolls having adjacent peripheral portions provided with registering complementary grooves varying in depth and radius of curvature from a minimum to a maximum depth and radius of curvature at circumferentially spaced locations, at least one of said rolls having a metal extruding groove in its concaved periphery disposed in anguiarly demarked relationship with respect to the surface of said periphery and extending in a spiral course about the axis of said roll in conformity to the fin desired on the finished product and registerable with the rib of said arbor.

26. The method of forming throughout a substantial portion of the length of a metal tubular structure,. a fin having successive longitudinally adjacent portions of different cross-sectional shapes; which comprises internally supporting said structure on an arbor having a rib extending outwardly from its periphery, forming a fin from some of the metal of the wall of said structure by pressing some of said metal with the aid of said rib into a confining fin forming recess corresponding at successive sections to the desired sections of said fin during axial movement 

